The planar surfaces of brake discs and other rotors are commonly ground flat by means of a motor driven grinding attachment mounted on the lathe housing. A grinding attachment of this type is described in U.S. Pat. No. 3,456,401 assigned to the assignee of the present invention.
In order to provide a swirl-like finish on the braking surfaces of a brake disc mounted on the lathe spindle, the prior art grinder attachment must be mounted to the lathe in proximity to the brake disc and is actuated to rotate the grinding disc while the brake disc is being rotated by the lathe. A considerable amount of set-up time is thus required to use such an attachment, and only a single swirl pattern can be obtained, it being dependent on the relative angular velocities of the brake disc and the grinder attachment. It would be desirable to reduce this set-up time, to enable the operator to select different swirl finishes, and also to reduce the manufacturing cost of the grinder attachment.